ENDOTHIA PIGMENTS 247 
against standard alkali with phenolphthalein as an indicator. The results 
for the three methods are given in table 3. 
Table 3. Determination of the Acetic Acid Liberated from Acetylendothine Red 
Method Used 
Weight of 
Acetyl Comp. 
BaS04 
C2H4O2 
C2H4O.2. 
Percent 
1st 
.8986 
.3012 
.2723 
•2253 
.8122 
.1425 
.1275 
.1029 
46.45 
47.34 
46.80 
45.68 
46.57 
30.78 
50.64 
64.52 
2d ■ 
2d 
3d 
Arithmetic mean of four determina- 
tions 
Required for 
C7H404(C2H30) 
C7H304(C2H30)2 
C7H204(C2H30)3 
The percentage of endothine red in the acetyl compound was determined 
by weighing the pigment regenerated in the last of the three processes 
mentioned above for the determinations of the acetyl groups in the com- 
pound, as the pigment is only slightly soluble in dilute sulphuric acid. 
This percentage was also determined by another method^^ which consisted 
in hydrolyzing the diacetylendothine red in a small volume of acetic acid to 
which a little sulphuric acid was added. When the mixture was allowed to 
stand for a short time, red crystals began to separate out. By adding the 
mixture to several volumes of water and allowing it to stand twenty-four 
hours the separation was completed. 
Table 4. Percentage Yield of Recovered Endothine Red from Acetylendothine Red 
Method Used 
Weight of Acetyl 
Compound 
Recovered Pigment 
Endothine Red, 
Percent 
1st 
.4532 
.1572 
■2253 
.2938 
.1014 
64.82 
64.50 
64.66 
64.66 
78.97 
64.55 
54.48 
2d 
2d , 
.1457 
Arithmetic mean of three determinations 
Required for 
C7H404(C2H30) 
C7H304(C2H30)2 
C7H204(C2H30)3 
The recovered endothine red was obtained as a "Brazil red" crystalline 
powder whereas the original coloring matter possessed a "ferruginous" 
color. On this account it was first thought that the recovered pigment had 
suffered a change in the process of hydrolysis. To decide this point the 
behavior of the two was studied more in detail. Both gave an "apricot 
orange" streak and acted in the same way toward such reagents as ferric 
chloride, dilute alkalis, sodium carbonate, and acids, and showed no dif- 
ferences when examined through the spectroscope. A spectral transmission 
Perkin, Arthur G. Luteolin. Part I. Journ. Chem. Soc. (London) Trans. 69: 
206-212. 1896. 
